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Neutrino experiments: Review of Recent Results

Neutrino experiments: Review of Recent Results. Junpei Shirai Research Center for Neutrino Science Tohoku University (for the KamLAND Collaboration). Tau04, 8th International Workshop on Tau-Lepton Physics, Nara, Sept.16, 2004. Contents:. Neutrino Oscillation Experiments

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Neutrino experiments: Review of Recent Results

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  1. Neutrino experiments: Review of Recent Results Junpei Shirai Research Center for Neutrino Science Tohoku University (for the KamLAND Collaboration) Tau04, 8th International Workshop on Tau-Lepton Physics, Nara, Sept.16, 2004.

  2. Contents: Neutrino Oscillation Experiments Solar and Reactor Neutrino Results Atmospheric Neutrino Experiments Coming experiments Double beta decay & Search for neutrino mass Summary

  3. Neutrino Oscillation Experiments: Fn Fn dEn Long history (40~50years!) of challenging n mass! Survival probability of na:  n P(nan)=1- P(nan) L DMij2L 1-sin22qsin2 ( ) <1 ? [Source] [Detector] 4E DMij2=Mi2 -Mj2)  ni cosq sinq = Oscillation parameters determined by  j -sinq cosq Flavor eigenstates Mass eigenstates * Tiny s, Mn=0 (SM) Clear evidence of n-flavor change; Flavor change of n occurs dominantly by Oscillation. Solar n: SNO Reactor n : KamLAND Atmospheric n : SuperK Accelerator n : K2K ndoes have a Mass!

  4. Solar Neutrino Problem (SNP) 4p+2e-4He+2ne+26.73MeV-En ne (Pure ne flux is generated by thermo-nuclear fusion in the center of the sun!) ne ? [Sun] [Earth] n flux: Observation < Prediction [Experiments] [SSM]

  5. Neutrino generation & spectrum [SSM] J.N.Bahcall Flux@1AU(/cm2/s/MeV), (/cm2/s for lines) 8B only pp-chain(98.4%) +CNOcycle(1.4%) Kamio-kande, SuperK SNO pp & above 7Be & above ppden pe-pdn pp ( .909) pep (2.110-3) pd3He g He H 4He 2p He p 4He e+n hep (10-) He HBe  Be p B Be e- Li n 7Be (.10-) 8B (.10-) BBe* e+n Li p2He 24He

  6. Solar n experiments (PDG’04) Fobs/F[SSM] ‘60 Radiochemical 0.3 0.4 0.5 0.6 Real time ‘68~ Homestake ‘70 ne+37Cl37Ar+e- First observation of solar n [C2Cl4] ‘80 [H2O] ‘83~’96 n really comes from the sun Kamiokande n+e- n+e- Establish Solar-n deficit ‘91~’97 ‘90~’01 ‘90 Gallex/ SAGE ne+71Ga71Ge+e- GNO Detection of pp n ‘96~ SuperK n+e- n+e- [H2O] High Precision measurement ‘00 ‘99~ SNO ne+dp+p+e- n+d n+p+nN n+e- n+e- neonly Active Non-ne Components ! ne+n+nt [D2O]

  7. SNO Neutron detection ; n+d H+g(6.25MeV); 0.5mb (~’01) n+Cl Cl+g’s(8.6MeV); 44b (~’03) n+He p+H; 5330b, event/event (’04~) fCC /fNC= e(e+m+ ) fCC /fES= e[e+0.154(m+ )] FSSM=5.05+1.01 -0.81 First evidence of Active Non-ne component. n+e- n+e- PRL 89, 011301(‘02) ne+dp+p+e- n+d n+p+n Fmt F (106cm-2s-1) (106cm-2s-1) Fne)=1.76±0.06(stat) ±0.09(sys) Clear deficit of Fne) F=5.09+0.44(stat)+0.46(sys) F: Excellent agreement with SSM. -0.43 -0.43 Oscillation looks very promising, but several solutions of DM2 and q for SNP!

  8. n-Oscillation parameters 22EGFNe sin22q -cos2q DM2 Four solutions to SNP Allowed region(95%) VAC(just so) H.Murayama SMA, LMA, LOW by Matter effect (MSW effect) P(nene)=1-sin22qsin2(DM2L/4E) e only] sin22q Seasonal variation, D/N asymmetry, Energy Spectrum ; LMA looks very promising, but no single experiment uniquely determined the solution. Needs decisive experiment ! Man-made n provided by Reactor.

  9. Reactor neutrino experiments Long history since the first detection of neutrino by F.Reines and C.L.Cowan using a reactor in 1950s. Power reactors as a n source. n Neutron rich nuclei to X b decay. A n ne emission + ~200MeV 235U, 239Pu, 241Pu, 238U Y /fission 102 ! Typical reactor : 3GW(thermal energy) Pure and intense  flux which is known < 2% ! Measure P(nene) with a distant detector.

  10. Previous reactor results e flux, s and interaction energies ne interactions ne flux (nepe+n) No oscillation was found! 3 4 5 6 7 8 En(MeV) Threshold (1.8MeV) Ed DM2>10-3 eV2 DM2~10-5eV2 to check LMA, 2pE Loscil= ~O(100)km DM2 Intense ne source & Large Detector are crucial! KamLAND ne spectrum of each fuel element is experimentally known or calculated (~2%).

  11. KamLAND Experimental Area Detector 1000m SuperK Control Room 2.2km Kamioka mine Nitrogen Gas System Water Supply System Oil Purification System

  12. KamLAND Detector 52 power reactors in Japan (Kamioka Liquid scintillator Anti-Neutrino Detector) 2700m w.e. ~0.3 m’s/sec 1000ton Ultra pure LS in a 13mf Balloon KamLAND 20m ~70GW(thermal) within 175±35km from KamLAND. 7% of the total reactor power in the world ! PMTs (in 2.5m thick mineral oil; 1325 17”(st~1.5ns) +554 20” (34%4p) DE/E~7.3%/E[MeV] ~106ne/cm2/sec @KamLAND Water Cherenkov counter(225 20”PMTs) (En>1.8MeV)

  13. Reactor Neutrino flux at KamLAND 235U 239Pu 238U 241Pu Typical reactor operation Thermal Power 1106ne/cm2/sec (En>1.8MeV) Burnup Total Fission Rates Wakasa Bay Kashiwazaki Others Shika Mar’02 Hamaoka Korea Jan’04 Fn is precisely estimated within ±3.4% Reactor power 2.1%, Fuel comp.1.0% n-spectra 2.5% Fission rates are calculated by thermal power and initial fuel composition.

  14. e Detection: epe+n Traditional method since F.Reines used Liquid Scintillator as an active target ! g(0.51) [Prompt e+ signal] e e- e+ Ee+(=En-0.8MeV) p [En1.8MeV] g(0.51) n g (2.2) [Delayed g by neutron capture] p ~200ms Correlated signals; (Energy, Position, Time) d Greatly removes backgrounds! e; ID, En, time, position ~100s(eeee)recisely known (0.2%)

  15. KamLAND:Vertex and Energy Calibration 12B/12N(4~15MeV) Z--deviation(cm) ±5cm Fiducial Fid vol.(R<5.5m) (R/6.5m)3 Z-position -ray sources along the central z-axis (Nfid/Ntot)/(Vfid/Vtot) Off axis by -spallation Total vol. Energy dependence Fiducial vol. Error = 4.7% ±2% DE/E n p n12C Energy threshold(2.6MeV Prompt signal) = 2.3% 68Ge,60Co, 65Zn 12B/12N

  16. KamLAND: Event Selection m Prompt event New Analysis! * Data sample: 766.3 ton yr (Mar.9,‘02~Jan.11,‘04) 4.7 times larger statistics than the 1st results Correlated events : Time, Distance & Energy of Delayed events RBalloon=6.5m 0.5ms<DT<1ms DR<2m Edelay=1.8~2.6MeV Eprompt-e+=2.6~8.5MeV RFid=5.5m Delayed event Reject geo-n Fiducial cut: R[prompt], R[delayed]<5.5m Reject m-spallation(9Li/8He rejection): 3m cylinder from the m Whole detector m 9Li/8He bkg: 4.8±0.9 events [non- showering m] [showering m

  17. Results analysis region Observed ne :258 Expected for non-oscillation : 365±24 Background : 7.5±1.3 [>2.6MeV] 9Li/8He: 4.8±0.9 Fast neutrons: <0.89 Accidental: 2.69±0.02 (Nobs-Nbkg) NExpected = 0.686±0.044±0.045 (stat) (sys) Clear disappearance at 99.995%CL 2.6MeV 2.6MeV Best-fit oscillation parameters sin22 = 0.83 m2 = 8.3×10-5 eV2

  18. Results Observed ne :258 Expected for non-oscillation : 365±24 Background : 7.5±1.3 [>2.6MeV] 9Li/8He: 4.8±0.9 Fast neutrons: <0.89 Accidental: 2.69±0.02 (Nobs-Nbkg) NExpected = 0.686±0.044±0.045 (stat) (sys) Clear disappearance at 99.995%CL No-oscillation 2.6MeV Scaled No-oscillation Excluded at 99.9%CL Null Oscillation Hypothesis disfavored Combined : 99.99996%

  19. L/E plot to check Oscillation or other hypotheses Best Fit Oscillation Barger et al., PRL82,(‘99) 2640 E.Lisi et al., PRL85,(‘00) 1166 Excluded at 96.5% Decay : cos2q+sin2qexp[-mL/(2tE)] Decoherence: 1-(1/2)sin2 2exp[-gL/E] Excluded at 98.3% Neutrino Oscillation is the best to fit the data!!

  20. 1st results Oscillation Analysis with 2 flavors delayed A New Background source (a,n) ! prompt 5.4MeV 222Rn 210Pb210Bi210Po a+13C  n+16O*(6.13, 6.05) 3.8d 22.3y 5d 138d npd g n+12C 12C*(4.4) +n 206Pb (stable) Excluded (95%) LMA2: excluded at 99.6%CL LMA New results Excluded (95%) Solar LMA Best fit (in LMA1) sin22q=0.83 Dm2=8.310-5 Best fit sin22q=1.0 Dm2=6.910-5 LMA0: excluded at 94%CL PRL 90, 021802(2003) Possible background sources; (g,n), spontaneous fission of 238U, NC reaction by atmospheric n, NC reaction by solar n on deuterons

  21. Global Analysis of KamLAND+ Solar tan2q=0.40+0.09 -0.07 Dm2=8.2+0.610-2eV2 -0. Mixing angle New 13C(a,n)16O Background ~10events n2004) Mass difference Preliminary KamLAND has shown decisively noscillation of LMA and DM2 has been measured very precisely!!

  22. SK Atmospheric neutrino oscillation cos  cos  cos  cos  SK-I (1496days; 1996-2001): Zenith angle distribution m-like Best-fit & Contours m-like e-like E.Kearns (n2004) Up-going stopping through Oscillation explains quite wl ! Strongly disfavored null oscillation! Up Down

  23. SuperK L/E Analysis SK-1 L/E Analysis K2K SK-1 All Data Select events with best L/E resolution To observe oscillation pattern! Further constraint on Dm2 2726 events by a cut of 70% resolution Dm2=(1.9~3.0)10-3eV2 sin22q>0.90 at 90%CL Best fit: (sin22qDm2)= (1.02, 2.4 10-3eV2 ), c2=37.7/40 dof  decay  decoherence • oscillation, dip at ~500km/GeV Dip: checked by Other L/E resolution Different binning of L/E Change of the direction vector E-like event  Decay rejected at 3.4s  Decoherence rejected at 3.8s

  24. q13 and CP in lepton sector ne c13 c12 s12 1 0 0 0 s13e-id 0 n1 = 0 c23 s23 0 -s12 c12  1 0 0  0 -s23 c23 -s13eid c13 0  0 0 1  ne 3 mixing angles; q12, q23, q13 Three Mass differences; DM213~DM223>>DM212   CP-violating phase d PMNS-matrix cij=cosqij Atmospheric n K2K Reactor n Solar n sij=sinqij New challenge !! * Present limit: sin22q13<0.12(CHOOZ) Reactor and LBL-Accelerator approaches are complementary!

  25. Reactor & LBL-accelerator experiments. (Mi2- Mj2)L Dij 4En DM122 - p DM232 2 Reactor : P(nene) -c134sin22q12sin212 -s122sin22q13sin232 -c122sin22q13sin231 D32D3 cij=cosqij , sij=sinqij D32D3D Reactor , L~O(1)km to make sin232, 10-3 P(nene)=1 - sin22q13 [Pure q13 measurement !] Accelerator : P(nmne) ~1 (taking L~2pEn/DM322) = sin22q13sin2q23sin232 cosq13sin2q12sin2q23sin2q13sin ~0.04

  26. LBL & Reactor LBL-Accelerator. Measurement sin2q23={1±1-sin22q23}/2 0.61 0.39 ex) sin22q23 =0.95 (Lower lim. SK) sin2q23 =0.61, 0.39 P(nmne) Reactor Measurement sin22q13 sin2q13sind LBL-accelerator experiment alone; Intrinsic uncertainty from sin2q23 and sindambiguity to determine sin22q13 Reactor q13 measurement solves them. sin22q13 provides the observability of the d.

  27. Kaska: Reactor 13 measurement KashiwazakiNuclearPower Plant (Japan); 24.3GW(World’sLargest thermal power!) 2 Near detector [Detector] ~400m Depth: 200m(far), 70m(near) Far detector 1300~1800m Gd-LS epe+n Delayed (~30ms) prompt 7 reactors ’s~8MeV (Gd) 40,000events/2yr (Far det.) Sys. Error 0.5~1%(<1%(det)+ 0.2%(flux)) Non-Gd LS 6m Buffer oil Sensitivity: sin22q13~0.017-0.026

  28. Search for 0nbb decays   cij =cosqij , sij =sinqij Nuclear process A(Z) A(Z+2)+2e- +2ne (DL=2) Nuclear Matrix element A(Z) A(Z+2) W W (T0n)-1=G0n|M0n|2 |<m>|2 Majorana Effective Majorana mass Phase space factor e- e- Majorana CP phase 3 |<m>|=|SUei2mi|=|m1c122c132+m2s122c132e2i+m3s132c132e2i | i=1 It is related to the neutrino mass scale. Mass hierarchy; m1m2m3[NH], m1m2m3 [IH], m1m2m3 [QD] 0nbb is very important. If found, DL=2 process, Majorana neutrino, |<mbb>| constrains neutrino mass patterns !!

  29. |<m>| & n mass hierarchy Dm2atm~50meV sin2qsolDm2sol~5meV |<m>| > a few10meV Inverted hierarchy PDG’04 |<m>|=|m1c122+m2s122e2i  +m3s132c132e2i | 1.00 Degenerate m1~m2~m3 0 0.10 Inverted Hierarchy m1~m2>m3 Effective mass |<m>| (eV) 0.01 Normal Hierarchy m1~m2<m3 Sensitivity of 1 0.001 would make a breakthrough ! Mass pattern and minimum  mass 0.001 0.010 0.10 1.00 Minimum neutrino mass (eV)

  30. Key for 0nbb Search b bb N t e (T0n1/2 /ln2) a e T0n1/2 4.11026 A M t 1 BDE |<m>|= [T0n1/2G0n|M0n|2]1/2 Qbb5 b appears as a sharp peak at the highest energy of the 2b spectrum in 2nbb decays. Sensitivity (Lower limit of T0n1/2[y]) A; atomic weight, a; Abundance M; Total mass [kg] # of nuclei=(M/A)NAa103 running time; y Detection efficiency [Signal] [BG] BM t DE Energy resolution;KeV Background rate; counts/kg/KeV/y

  31. Lots of Challenges to 0nbb M ae , Qbb BDE Tracking 150Nd DCBA MOON NEMO EXO Cryogenics 100Mo CUORE/CUORETINO COBRA GEM GENIUS Majorana MPI 82Se 113Cd, 123Te 136Xe Bolometory 76Ge Foils in wire chamber, TPC, Mag. field Ionization (LN2) 116Cd Scintillation Making large figure of merit CAMEO CANDLES CARVEL GSO Xe 48Ca 116Cd 160Gd to reach |<mbb>|~100-10 meV in several years operation! 136Xe Crystals in Liq. Scint.

  32. Direct n mass measurement dN/dEe=KF(Ee,Z)peEtot(E0-Ee)[(E0-Ee)2-mn2)]2 Use only kinematics of decay particles to measure missing mass. (cf. n-oscillation, 0nbb, astrophysics) The fact of large flavor-mixing of n Properties of n’s (incl. mass) might be the same. Mass degeneracy can be checked with a sensitivity of sub-eV. Tritium b-decay has been tried : Small endpoint energy (18.6keV) Super-allowed transition Final state spectrum of daughter molecules are well known. dN/dE mn=0 mn0 Troitsk m<2.05eV(@ 95%CL) Mainz m<2.2eV (@ 95%CL) PLB350(‘95)263. E0-Ee PLB460(‘99)219. E0 Both uses magnetic-bottle spectrometer and gaseous 3H target.

  33. -mass sensitivity: 0.2eV KATRIN (Karlsruhe Tritium NeutrinoExperiment) Electrostatic spectrometer with Adiabatic magnetic collimation Windowless gaseous tritium source Large acceptance, High resolution =Etrans/B : conserved in adiabatic B field DE/E=Banal/Bmax : Energy resolution (Banal ~a few mT, Bmax~6T) ~70 m beamline, 40 s.c. solenoids Stainless steel vessel(10m

  34. A claim for discovery of 0nbb Highest Sensitivity, Select single site events by PSA Degenerate! Can be found by direct measurement with sub-eV sensitivity and planned 0nbb experiments! (H.V.Klapdor-Kleingrothaus, n2004) Needs confirmation by coming experiments!

  35. Summary Recent n experiments have established n oscillation by observing the flux deficit, flavor change and spectral distortion; Solar n (SK/SNO)/Reactor n (KamLAND) for ne (ne), Atmospheric n (SK)/Accelerator n (K2K) for nm Oscillation parameters, q12, q23, DM122, DM232 are being determined precisely by ongoing experiments. Reactor 13 measurement is very important to the coming LBL experiment aiming to measure CP-violating phase d experiment is crucial not only to know whether n , but constrain or determine mass pattern, if |<mbb>| sensitivity to ~0.01eV is attained. remass search with a mass sensitivity of sub-eV can have a discovery potential.

  36. Backup slides

  37. Solar n problem Atmospheric n anomaly oscillation ! Mn0 Precise measurement of oscillation parameters. Planned bb, LBL experiments Absolute n mass? Mass pattern? CP & Mixing mechanism?

  38. Sudbury Neutrino Observatory Deep underground 6010m w.e. 1000ton D2O in 12mf acrylic vessel 9600 PMTs (60%of 4p) H2O (1700ton inner shield +5300ton outer shield) Urylon Liner and Radon Seal

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